438 MR. C. H. 0’ DONOGHUE ON THE 
venosus. In the adult Scylliwm and Mustelus the vessel opening 
into the posterior cardinal vein in the position of that described 
by Rabl as the * sub-clavian ” is really the sub-scapular. 
In an embryo of 56 mm. it is quite easy to trace the relations 
of these two vessels, which are found to be the same as in 
the adult. The sub-clavian vein, formed by the union of 
the brachial and lateval abdominal veins, opens into the sinus 
venosus on its ventral side nearer the middle line than the 
opening of the anterior cardinal sinus. The sub-scapular vein, 
into which the lateral cutaneous vein opens, joins the posterior 
cardinal vein in about the position indicated by the ‘‘ sub- 
clavian ” vein of Rabl. 
A sub-clavian vein is figured by Grosser (2 a, p. 184, fig. 4) in 
the same position in an embryo of only 26 mm., although its 
relation to the brachial and lateral abdominal veins is not shown, 
nor is it identified as sub-clavian. 
Rabl himself says (11, p. 233): “In den proximalen Theil 
des Cardinalvenensinus miindet die Vena subclavia ein. Aus- 
serdem tritt in die untere Wand des Ductus Cuvieri eine 
Vene, die nach hinten bis zu den Bauchflossen zu verfolgen ist, 
und deren Lage unter der Musculatur der vorderen Bauchwand 
es nicht zweifelhafterscheinen lisst, dass man es hier mit der 
Parietal-oder Seitenvene zu thun hat. Auf diese Vene habe ich 
im Szshema keine Riicksicht genommen.” 
It will be seen, then, that Rabl recognises two veins, but I 
venture to think that ne has misinterpr eted one of them and in 
ealling it the sub-clavian vein has suggested a connection with 
the pectoral fin which does not exist. A muddle, probably re- 
sulting from this, is to be found in nearly all the text-book 
descriptions of Scyllium, in which it is stated that the sub- 
clavian vein enters the lateral border of the front end of the 
posterior cardinal sinus and brings back blood from the pectoral 
fin. In all Elasmobranchs described, and also in Seylliwm, the 
blood is returned from the pectoral fame by the brachial veins. 
These open into the lateral abdominal veins, and the common 
trunks so formed, which may be justly fommed sub-clavian veins, 
open into the deans Cuvier. 
For descriptive purposes it is easy to divide the venous system 
according to its derivation from the embryonic condition just 
described into pre-cardiac vessels, post-cardinal vessels, and sub- 
intestinal vessels, to which must be added the lateral veins, the 
coronary veins, and the cutaneous veins. 
III. Tse Pre-CarpiAc VESSELS. 
1. The Orbital Sinus. 
1. i. The Nasal Sinus. 
1. 1. The Orbito-Nasal Vein. 
J.in. The Anterior Cerebral Vein. 
l.iv. The Inter-Orbital Vein. 
